Heat-resistant, austenitic cast steel and exhaust equipment member made thereof

Abstract

Exhaust equipment members are made of a heat-resistant, austenitic cast steel with excellent castability and machinability having a composition consisting essentially, by weight, of 0.2-1% of C, 2% or less of Si, 2% or less of Mn, 8-20% of Ni, 15-30% of Cr, 0.5-6% of Nb, 1-6% of W, 0.01-0.3% of N, optionally 0.01-0.5% of S, C--Nb/8 being 0.05-0.6% and the balance being Fe and inevitable impurities.

What is claimed is: 
     
       1. A heat-resistant, austenitic cast steel with excellent castability and machinability, said austenitic cast steel having a composition consisting essentially, by weight of: C: 0.2-0.6%   C--Nb/8: 0.07-0.3%   Si: 0.3-1.5%   Mn: 0.3-1.5%   Ni: 8-15%   Cr: 17-25%   Nb: 1-4%   W: 2.66-4%,   N: 0.03-0.2%, and   Fe and inevitable impurities: balance.   
     
     
       2. The heat-resistant, austenitic cast steel with excellent castability and machinability according to claim 1, wherein W is partially or totally substituted by Mo at a weight ratio of W=2Mo. 
     
     
       3. A heat-resistant, austenitic cast steel with excellent castability and machinability, said austenitic cast steel having a composition consisting essentially, by weight of: C: 0.3-0.6%   C--Nb/8: 0.07-0.3%   Si: 0.3-1.5%   Mn: 0.3-1.5%   Ni: 8-15%   Cr: 17-25%   Nb: 1-4%   W: 2.66-4%,   N: 0.03-0.2%,   S: 0.03-0.25%, and   Fe and inevitable impurities: balance.   
     
     
       4. The heat-resistant, austenitic cast steel with excellent castability and machinability according to claim 3, wherein W is partially or totally substituted by Mo at a weight ratio of W=2Mo. 
     
     
       5. An exhaust equipment member made of a heat-resistant, austenitic cast steel with excellent castability and machinability according to claim 2. 
     
     
       6. The exhaust equipment member according to claim 5, wherein said exhaust equipment member is an exhaust manifold. 
     
     
       7. The exhaust equipment member according to claim 5, wherein said exhaust equipment member is a turbine housing. 
     
     
       8. An exhaust equipment member made of a heat-resistant, austenitic cast steel with excellent castability and machinability according to claim 6. 
     
     
       9. The exhaust equipment member according to claim 8, wherein said exhaust equipment member is an exhaust manifold. 
     
     
       10. The exhaust equipment member according to claim 8, wherein said exhaust equipment member is a turbine housing.